Study of the modulation of lipid bodies in epithelial cells.

by Souza Moreira, Luciana de

Abstract (Summary)

Lipid Bodies (LBs) are cytoplasmic inclusions manly formed by triglycerides and cholesterol esters, being also intracellular deposits of arachidonic acid (AA), which can bemetabolized for generation of eicosanoids. PGE2 is the major AA metabolite produced by epithelial cells. It is a potent mediator of cell motility, survival, proliferation and angiogenesis,all central processes to restoration of epithelial tissue homeostasis after injury. Our aim was to investigate LBs biogenesis and their role in AA metabolic pathway in epithelial cells. Specifically we evaluated: i) induction of LBs by inflammatory mediators; ii) intracellular signaling pathways involved in such induction; iii) and modulation of LBs during cellproliferation and migration. We used IEC-6 as experimental model, a cell line derived from rat normal intestinal epithelium. LBs were evaluated under light microscopy after staining byosmium tetroxide. Protein expression level was assessed by western blotting, and PGE2 generation determined by EIA in cell culture supernatants. IEC-6 cells cultured subconfluentlyin DMEM supplemented with 5% fetal bovine serum (FBS) presented 15-20 LBs/cell. FBS withdraw or reaching confluency eliminated LBs. FBS-induced LB biogenesis in sub-confluent cells was blocked by ERK1/2 and p38 inhibitors. Stimulation of confluent IEC-6 by IL-1b, PAF and PMA was unable to induce LBs. In contrast, addition of AA dosedependently-induced LB formation, independent of its metabolism to PGE2, and proliferation foci in confluent cells. LBs formation induced by AA was dependent on signaling through p38, PKC and PI3K, but not on ERK 1/2 or JNK. LB biogenesis by epithelial cells facilitates AA release after activation without changes in cytosolic phospholipase A2-a (cPLA2-a) expression. Altogether, our results suggest a strong relationship between LB biogenesis and cell proliferation, and indicate that such organelles are induced in a stimulus-specific manner and facilitate AA mobilization in epithelial cells.